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SM-4.75 asphalt mixtures incorporate a 4.75-mm nominal maximum aggregate size along with a corresponding fine gradation that accommodates higher liquid asphalt contents, which promotes durability. The SM-4.75 materials are suited to take advantage of the lower cost finer fractions of the stone-crushing process. The fine gradation also permits very thin applications (19 mm to 25 mm), thereby reducing the quantity and cost of materials, as well as construction time. Mixtures with 4.75-mm nominal maximum aggregate size have the potential to improve riding quality, extend pavement life, increase durability, and reduce permeability and road-tire noise. This study evaluated the laboratory cracking performance of SM-4.75 mixtures. It was done through sampling and testing of plant-produced mixtures that were placed on low volume traffic routes. Several tests were used to characterize the mixtures including the simplified viscoelastic continuum damage test, indirect tensile asphalt cracking tests, the semi-circular bend test, and the overlay test. Laboratory cracking tests indicated that SM-4.75 mixtures are crack susceptible and would benefit from higher binder contents. However, field performance data for the tested mixtures are needed to validate the crack susceptibility of the mixtures. In general, laboratory performance ranking order among different tests is not consistent for different mixtures. Binder testing results indicated that the majority of the mixtures should be resistant to non-load related cracking, even though the mixtures contained 20% and 30% recycled asphalt pavement.

As transportation agencies are adopting proactive pavement friction management using continuous friction measurement equipment (CFME), the need for a method that allows interconversion between the traditional locked-wheel skid testers (LWSTs) becomes important to assure continuity with past practices. This paper evaluates several conversion methods based on the International Friction Index (IFI) approach and proposes an alternative method that allows predicting the measurements of the LWST using measurements with the Sideway-Force Coefficient Routine Investigatory Machine (SCRIM). The investigation is based on data collected using a SCRIM and two LWSTs on a controlled pavement test facility. The results suggest that a conversion based only on the speed adjustments (FR60) is the most effective method to predict the LWST measurements from SCRIM measurements. The coefficient of determination and average absolute error are comparable to those using the full IFI F60 formula but do not require static reference measurements. The study also showed that the three tested devices produced appropriate repeatability as computed using the limit of agreement at the three tested speeds and on a wide range of surfaces.

In 2015, the Virginia Department of Transportation (VDOT) proposed changes to their specification for asphalt mix design. The changes incorporated a reduction of design gyrations from 65 to 50; the addition of constraints on the No. 4 (4.75 mm) and No. 30 (600 µm) sieves; and adjustments to the production value for voids filled with asphalt and minimum voids in mineral aggregate. Before these modifications were fully adopted, a study was performed to assess the effect of the changes on mixture properties and laboratory performance. Eleven pairs of asphalt mixtures were evaluated; the pairs consisted of a typical VDOT 65-gyration mixture produced under the specification current at the time and a companion 50-gyration mixture designed and produced in accordance with the proposed specification. Mixtures were evaluated to determine the effect of the design parameters on volumetric properties, gradation, and permeability. The changes had very little effect on volumetric properties or gradation. Permeability effects were mixed, with 9.5 mm nominal maximum aggregate size mixtures requiring greater compaction to meet permeability requirements and 12.5 mm nominal maximum aggregate size mixtures showing improved permeability even at higher air-void contents. For the 50-gyration mixtures, core air voids were reduced, indicating the potential for increased durability attributable to improved densification in the field.

Adequate macrotexture characterization is an essential objective for transportation practitioners because primary pavement surface characteristics like friction, tire–pavement noise, splash and spray, and rolling resistance are significantly influenced by pavement macrotexture. This paper proposes an enhanced macrotexture characterization index based on the effective area for water evacuation (EAWE) that better estimates the potential of the pavement to drain water and provides improved correlations with two properties of pavement surfaces that are predominantly affected by macrotexture: friction and noise. A three-step methodology is proposed to compute the index: ( a) a spike-removal procedure that assures the reliability of the texture profile data; ( b) an enveloping profile calculation, which is necessary to delimit the area between the tire and the pavement when contact occurs; and ( c) a definition of the EAWE, which serves as the index for characterizing macrotexture. Comparisons of current mean profile depth (MPD) and proposed EAWE macrotexture indexes by using 32 pavement sections confirmed that MPD overestimated the effective area for water evacuation between a tire and the pavement surface. Correlations for MPD and EAWE indexes with tire–pavement friction and noise were performed, and measurable improvements in correlations were achieved. Results show that it is possible to define a promising index on the basis of the EAWE that realizes advantages over MPD.

A comprehensive pavement management system includes a pavement friction management (PFM) program to ensure that pavement surfaces are designed, constructed, and maintained to minimize friction-related crashes in a cost-effective manner. FHWA Technical Advisory 5040.38 on PFM canceled a previous advisory that focused only on the reduction of wet skid crashes. This new advisory recommends continuous friction measuring equipment as an appropriate method for evaluating pavements. The study described in this report developed a pavement friction inventory by using the GripTester. The friction data were then coupled with crash records to develop a strategy for network analysis to improve the ability to predict crash rates. The crash rate analysis applied a well-established methodology for the identification of areas of high crash risk by using safety performance functions (SPF), which included empirical Bayes rate estimation from observed crashes. The current Virginia Department of Transportation SPF models can be modified to include skid resistance and radius of curvature (Interstate and primary system only) to improve their predictive power. The same methodology was also used to contrast the effect of two friction repair treatments—an asphalt overlay and high-friction surface (HFS) treatments—to explore how their strategic use could affect network-level crash rates. The result suggests significant crash reductions with comprehensive economic savings ($100 million) when applied to a single relatively rural district. These findings easily justify an aggressive state-level PFM program and support continued research to quantify the influence of other pavement-related characteristics such as macrotexture, grade, and cross slope.

This paper summarizes findings from Virginia’s recent quieter pavement research. It reviews overall condition; functional performance (ride, noise, and friction); winter maintenance and use characteristics; and other important observations made about a series of demonstration projects constructed in 2011 and 2012. The lower-noise pavement technologies included porous asphalt, conventional diamond grinding, and Next Generation Concrete Surface. The paper also summarizes results from the accelerated trafficking of Virginia materials at the National Center for Asphalt Technology Pavement Test Track. Finally, the paper reviews current federal policy and the pertinent ramifications for Virginia’s program. As of spring 2015, the difference in measured tire pavement noise between control surfaces and the most successful (lowest noise) quiet asphalt technology was no longer detectable with normal human hearing (

Smoothness specifications are used by almost all state transportation agencies, including the Virginia Department of Transportation (DOT), to promote overall quality and optimum ride quality. The Virginia DOT has a ride specification that provides a pay adjustment (incentive or disincentive) depending on the smoothness of the final paved surface. The Virginia DOT’s ride specification also has a provision for waiving the disincentive and applying only the incentive part to projects in which project geometry and so on are perceived to make it difficult for the contractor to achieve the desired ride quality. When applied, the waiver is intended to encourage the contractor to apply additional effort to improve ride quality for otherwise difficult projects. In late 2011, the Virginia DOT’s executive leadership formed an Asphalt Quality Task Force to identify and recommend specific achievable measures to improve the quality of the asphalt paving in Virginia. The task force recommended assessing the feasibility of creating an incentive-only provision default for projects that would otherwise not qualify for application of the regular ride specification. This study documented and critically reviewed the pilot application of the incentive-only provision for rideability on selected asphalt resurfacing schedules for the 2013 construction season. In addition to the incentive-only sites, several lane miles of control sites were also considered. The purpose of the control projects was to compare them with the incentive-only sites to determine if the prospects of added incentives led contractors to alter their paving procedures in pursuit of a higher-quality ride. There was no statistically reliable distinction between the achieved quality of the incentive-only and control sites.

Evaluation of crash count data as a function of roadway characteristics allows departments of transportation (DOTs) to predict expected average crash risks to assist in identifying segments that could benefit from various treatments. Crash risk is modeled using negative binomial regression, as a function of annual average daily traffic (AADT) and other variables. For this paper, a crash study was carried out for the Interstate, primary, and secondary routes in the Salem District of Virginia. The data used in the study included the following information obtained from Virginia DOT records: 2010 to 2012 crash data, 2010 to 2012 AADT, and horizontal radius of curvature. In addition, tire–pavement friction, or skid resistance, was measured with a continuous friction measurement, fixed-slip device called a GripTester. Negative binomial regression was used to relate the crash data to the AADT, skid resistance, and horizontal radius of curvature. To determine which of the variables to include in the final models, researchers performed the Akaike information criterion test. By mathematically combining the information acquired from the negative binomial regression models and the information contained in the crash counts, researchers empirically estimated the parameters of each network’s true average crash risks with the empirical Bayes approach. The new estimated average crash risks were then used to rank segments according to their empirically estimated crash risk and to prioritize segments according to their expected crash reduction if a friction treatment were applied.

Lack of sufficient friction between tyre and pavement is known to be one of the contributing factors in vehicle crashes. The application of new technologies can be used to determine the low friction areas or vulnerable accident sites at both the project and network levels. Continuous friction devices are one of the newest systems currently used in European countries that have recently been introduced to the United States. Continuous friction measuring devices are designed to measure the friction under conditions similar to those produced by an anti-lock braking system. Although continuous friction measuring equipment (CFME) provides valuable information about surface friction, processing of the relatively large amount of data produced is time-consuming. Traditional methods such as comparing the average friction provide a quick and simple data analysis method; however, they neglect other important characteristics such as friction spatial variation and low friction spots. This study proposes a metho...

Transportation agencies devote significant resources toward the collection of highly detailed and accurate pavement roughness data by using profiler vans to support pavement maintenance decisions. However, these agencies often cannot afford to measure roughness annually for the whole pavement network. This study introduced an improved acceleration-based metric, an index normalized by vehicle operating speed, to be used on a regular basis to screen pavement segments that are likely to be deficient; then a profile van can be sent to accurately measure the roughness condition. A profile van collected pavement profile data on 50 mi (80 km) of roadway; these data were then used to calculate the international roughness index (IRI). Meanwhile, two tablet computers were placed on the vehicle floor to collect data, including three-way accelerations, GPS coordinates, and vehicle speeds. A normalized acceleration-based index was created by incorporating a speed factor. Furthermore, logistic regression models were created to evaluate the effectiveness of the proposed index in identifying deficient pavement sections [IRI ≥ 140 in./mi (2.21 m/km)]. The proposed acceleration-based metric was able to identify between 80% and 93% of all deficient pavement sections. This research points to the feasibility of using a cost-effective acceleration-based application for network screening, a process that will reduce the total mileage of pavement sections needing to be measured and meanwhile still identify locations for which maintenance work is necessary.

High-friction surface (HFS) treatments entail an application of epoxy and aggregate to roadway surfaces to provide a high degree of skid resistance. These treatments may be particularly effective in cases in which demand for tire–pavement friction is especially high, such as on rural asphalt roads at high risk for crashes, or with a record of crashes, or both, that may relate to lower skid resistance. In 2012, the Virginia Department of Transportation placed HFS materials at four locations that met this description. This paper provides information on the construction, skid resistance, bond strength, condition after 1 year, and cost of the Virginia HFS treatments. For comparison purposes, alternatives to HFS are briefly described also. The 2012 Virginia HFS installations were successfully constructed on time. The materials were of high quality and bond strength exceeded the tensile strength of the asphalt. Testing with continuous friction measurement equipment was particularly effective and served to con-firm high comparative skid resistance on the new surfaces. Unfortunately, the marginal quality of the underlying material is expected to limit the performance life of at least some of the HFS applications. For small applications, HFS treatments cost about the same as most alternative treatments used to increase skid resistance and provide the highest constructed friction. These materials may provide an effective tool in a systemwide pavement friction management program, but they will perform only as long as the structure that supports them. Pretreatment surveys with continuous friction measurement equipment can be coupled with project geometric characteristics to ensure appropriate limits on HFS applications.

This paper compares the potential short-term noise reduction generated by the use of two quiet concrete technologies [Next Generation Concrete Surface (NGCS) and conventional diamond grind] and three quiet asphalt surfaces (porous friction course surfaces with and without rubber and different maximum-sized aggregates) with control pavement sections (conventional transverse-tined portland cement concrete pavement and stone matrix asphalt pavement surface). The potentially quiet pavement surfaces were placed along five demonstration projects in Virginia. This paper investigates the susceptibility of the proposed surfaces to external factors, such as aging (four seasons were involved) and air temperature differentials. The statistical analysis of the collected data showed that all proposed surfaces presented benefits in terms of noise reduction; the NGCS exhibited noise reduction potential as high as 5 dB(A) when compared with the control section. For the asphalt surfaces, the sections with higher amounts of...

There are many devices used around the world to measure friction. The majority of Departments of Transportation in the USA currently use locked-wheel trailers for friction measurements. The use of the fixed slip devices has gained popularity in other countries, especially in Europe, and they are starting to be used in the USA. These systems measure the friction under the condition similar to those produced by anti-lock braking system. This paper evaluates the effect of grade, water film thickness and speed on friction measurements of the continuous friction measuring equipment. The data used in this study were collected at the Virginia Smart Road using the GripTester. The experiment showed that grade affects the GripTester measurements suggesting that measuring with GripTester would be more accurate on flat surfaces. It also confirmed previous results that measurements were shown to be sensitive to water film thickness and testing speed.

The first stages of the development of a formal quieter pavement use guideline for Virginia are described. Chronicled are the selection of lower-noise pavement technologies (i.e., quieter pavement [QP]); development and construction of the first season (2011) of QP demonstration projects and evaluation tools and analysis being used to compare the performance of the alternative strategies. After one winter of service, the lower-noise asphalt technologies were measurably (2 dB or less) less noisy than the control surfaces were on average and noticeably (≤3 dB) more quiet in several specific cases. The quiet concrete technology, the Next Generation Concrete Surface (NGCS), maintained a readily noticeable (5 dB) noise advantage over the control concrete surface. Beyond tire–pavement noise, the QP technologies have a distinct advantage over the control surfaces when it had came to achieved ride quality. The NGCS was very smooth, and contractors earned incentives for ride quality with the quiet asphalt materials, including (and especially with) the materials that were placed at a 1-in. thickness. Although some wheelpath consolidation was evident in the texture data for the asphalt technologies, all of the QP surfaces were exhibiting excellent skid resistance and were receiving consistent recognition for good wet-weather service.

Previous comparisons of pavement friction equipment focused on the harmonization of devices that measure pavement friction, but did not assess the agreement of the measurements between them. Harmonization was accomplished with normalization of the measurements through adjustment to a standard slip speed and use of macrotexture measurements in models of the friction–speed relationship. A problem with this procedure was that the true value of friction on which the comparisons were made was assumed. When true values remain unknown, valid comparisons between two devices require the use of agreement assessments. Limits of agreement (LOA) were used to compare two pavement friction devices. The first comparison was made with one run to illustrate LOA. A second comparison with two runs was made to gain understanding of their repeatability and use in LOA. A more complex LOA procedure was conducted with multiple runs of the two devices. The results of another study that used LOA between another pair of pavement friction devices showed a better agreement. The obtained LOA results showed a 95% confidence level, which was considered not adequate. A comparison between the 95% repeatability coefficients and the 95% LOA computed for the two devices indicated that factors other than repeatability were responsible for the lack of agreement. Use of the LOA method of analysis should be considered before harmonization of different devices. Predictive models based on correlation are not recommended for comparing pavement friction measuring devices.

A 4.75-mm nominal maximum aggregate size Superpave® mix developed by the Virginia Department of Transportation was placed as a thin treatment over existing, aged sections in an accelerated pavement test facility. Half the loaded wheelpath was paved with and half without the treatment to explore rutting susceptibility and quantify the ability to defer cracking. Loose mix was collected during construction to verify the mix design and for laboratory dynamic modulus, flow number, Hamburg wheel tracking, and axial fatigue testing. The mix was produced according to the volumetric specifications, but the in-place density was higher than the target. Although laboratory tests indicated poor resistance to rutting, full-scale performance illustrated that the total rutting in the treated sections was equal to or less than the total rutting in the sections without the overlay. Top-down cracking was significantly delayed as a result of the presence of the thin overlay, but once the pavement sections were aged and brittle, the treatment could not delay cracking.

The paper investigates the statistical measures of process mean, standard deviation, correlation, and normality assumptions for the Virginia Department of Transportation volumetric properties of voids in total mix (VTM), asphalt content (AC), and voids in mineral aggregates (VMA) on the basis of 3 years of contractors' testing data. The VTM had an overall pooled standard deviation of 0.86%, but the data distribution was found not to follow the normal distribution. No difference based on mix type [base mix (BM), intermediate mix (IM), surface mix (SM), or stone matrix asphalt (SMA)] was observed. The average AC, however, was found to depend on mix type with three distinct groups: BM and IM (about 4.35%), SM (about 5.30%), and SMA (about 6.40%). The standard deviations for the combined BM and IM and that of the SM were found to be similar (about 0.30%) and different from the standard deviation of the SMA (about 0.42%). The AC data distribution passed one of the three tests of normality. The correlation between the VTM and AC was found to be equal to −0.28. The average of the VMA was found to depend on mix type and specifically on the maximum nominal aggregate size ranging from 13.84% for the BM to 18.18% for the SMA. The standard deviations was found to be independent of mix type (about 1.00%). Similar to the VTM, the VMA distribution failed all three normality tests. As expected, a high correlation between the VTM and VMA was observed (about 0.65). The correlation increased to 0.85 when the effect of the AC was removed.

Locked-wheel trailers are the predominant friction-testing tool used by state departments of transportation in the United States. These trailers measure friction on a locked wheel on the wetted pavement surface as the wheel slides at a constant speed. The skid resistance is reported as the skid number (SN) at the speed it was measured, with the standard test speed at 40 mph. Speed on most rural interstate and primary roads is rarely lower than 65 mph, whereas in most urban environments, congestion, intersections, and high-traffic volumes can lead to average traffic speeds as low as 20 mph. A methodology was proposed to convert the skid numbers from one speed to any desired speed by using adjustment factors. The data used to develop this methodology came from measurements taken by members of the Pavement Surface Properties Consortium for the three consecutive years from 2007 to 2009. The adjustment factors were developed for the different flexible and continuously reinforced concrete pavement surfaces that are available at the Virginia Smart Road. The friction measurements performed with the skid testers presented different responses to the different pavement surface types. To separate them, principal component analysis was used, and three different groups of surfaces were identified. Principal component analysis was also used to develop a friction conversion method that used correlations between speed and texture. Correlations between speed factors and macrotexture were computed only for smooth tire skid testers, because ribbed tires do not exhibit good relationships, probably because measurements with this tire are not sensitive to macrotexture.

The Virginia Department of Transportation has worked toward end-result specifications (ERS) in hot-mix asphalt (HMA) since the mid-1960s. With the recent advances in HMA material characterization and the completion of the new Mechanistic–Empirical Pavement Design Guide (MEPDG) under NCHRP Project 1-37, the ultimate goal of true ERS that are performance related seems more feasible. The use of the HMA dynamic modulus as an HMA quality measure is investigated. An effective reduced frequency (temperature–frequency combination) at which the HMA dynamic modulus best correlates with the MEPDG-calculated HMA rutting is determined for eight climatic conditions. This effective reduced frequency did not coincide with the modified Witczak effective temperature–frequency equation. The effect of HMA layer thickness (51 to 254 mm) on effective reduced frequency was investigated for Roanoke, Virginia. It was found that layer thickness had a minor effect on effective reduced frequency, so that the latter can be assumed independent of layer thickness for all practical purposes. Finally, the HMA rutting calculated by using the effective reduced frequency was found comparable with the MEPDG-calculated HMA rutting with average and maximum differences of 6.5% and 23%, respectively. This difference is acceptable considering the variability in actual field rutting measurements (for the same conditions) as well as accuracy of the MEPDG in determining the average HMA field rutting. Use of the effective reduced frequency can result in considerable time and money savings, especially for quality assurance applications for which testing is regularly performed.

The preliminary findings on the design, production, placement, and early life performance of a new generation open-graded surface course [also referred to as porous friction course (PFC)] for use in Virginia are highlighted. The primary objective of the larger research project is the design of a functionally optimized asphalt concrete wearing course. Important aspects of the mix design and construction and the initial functional quality of the new surface are documented. General observations associated with the trial section and normal production and placement activities are accompanied by a summary of the quality characteristics of the material. Special emphasis is placed on the early life functional characteristics of the new wearing course. Among these key characteristics are ride quality, wet skid resistance, and tire–pavement noise. Observations made during trial production and placement led to lighter (thinner) recommended application rate and reduced asphalt concrete mix temperatures. Preliminary functional tests indicated that the PFC has exceptional early-age skid resistance, incentive-quality smoothness, and low tire–pavement noise. On the basis of initial cost and early-life functional performance, the PFC is cost-competitive with traditional mixes placed at traditional application rates (when those mixes are used for functional rather than structural improvement).

This paper presents a research effort to compare and harmonize measurements of texture and skid resistance taken with various devices at the Virginia Smart Road in May 2008 by the members of the Virginia Consortium for Pavement Surface Properties. There have been numerous efforts by different countries and agencies to understand better the relationship and behavior of different friction-testing devices and the influence of texture, speed, and other external conditions on these measurements. Measurements obtained with different types of equipment on 24 pavement sections with a wide range of textures were compared, and the relationship between friction and speed for the different pavement sections and devices was studied. Data were collected with two locked-wheel skid trailers, a Griptester, and a dynamic friction tester. Nine asphalt sections were tested; six were Superpave® mixes, two were stone matrix asphalt, and one was an open-graded friction course. The concrete sections tested included one continuously reinforced concrete pavement with tined finishing and two epoxy overlays. Even though all steps included in the specifications derived from the experiments by the Permanent International Association of Road Congresses (PIARC) were followed, the results obtained were not satisfactory. From a theoretical standpoint, all the values computed with the international friction index (IFI) F60 should be equal, but this was not the case. Discrepancies in the IFI values calculated for the different devices suggest that the original coefficients determined during the PIARC experiment may need to be adjusted for the devices evaluated, before the IFI can be implemented by the participating agencies.

This paper discusses the results of the field experimentation of a new system developed to help inspect the construction of asphalt pavements using digital video images. The system computes the gray-level co-occurrence matrix of images of newly constructed pavements to find various parameters that are commonly used in visual texture analysis. Using principal component analysis to integrate multivariable data into a single classifier, Hotelling’s T2 statistic, the system creates a list of the location of possible nonuniformities that require closer inspection. A total of 18 continuous road segments of recently paved roads were tested and analyzed with the system. These road segments allowed the refinement of the methodology and the software needed to produce tables and plots that will be used by inspection personnel in the field. The results demonstrated the capability of the system for detecting potential nonuniformities of recently completed pavements that can be used during construction as well as in th...

The Virginia Department of Transportation's (VDOT's) Road and Bridge Specifications combine with various special provisions to cover more than 13 asphalt concrete surface mix designations. Although the specifications offer recommendations about the types of mixes that should be programmed for a given set of facility characteristics, local conditions and experiences heavily influence the predominantly selected mix. As material prices continue to climb without budgets doing the same, local circumstances are more often going to contribute to the selection of the less expensive mixes, especially as long as managers lack a defensible rationale for specifying a more expensive option. This paper describes an economic analysis procedure designed to help engineers and managers select the most cost-effective mix. This procedure includes a methodology for estimating the expected service life for each mix, which is developed by using the systemwide condition ratings for all of Virginia's Interstate and state primary roads. Through the use of examples with typical project families, the research demonstrates that premium prices for stone matrix asphalt can generally be justified by better performance. In one illustration that uses actual condition and awarded price data, a life cycle cost analysis revealed that the use of stone matrix asphalt in lieu of dense-graded mixtures on Interstates might save VDOT more than $7,500 per lane mile in net-present-value costs.

Smoothness, the absence of bumps and dips in the riding surface of a pavement, improves the quality of the ride and is believed to prolong the life of the pavement. Research addressed the effect of Virginia's special provision for smoothness on contract prices for hot-mix asphalt. The research also examined the financial value of the resulting product (presumably smoother pavements). The analysis included maintenance cost savings for the owner–agency, as well as any reduction in delay and operating costs for the motoring public. A detailed statistical analysis found no statistically definitive effect on bid price as a result of the use of a special provision for rideability. A similar analysis on a more focused data set, however, did document a lifetime reduction in the international roughness index of almost 9 in./mi. This reduction in roughness (increase in smoothness) implies an increase in pavement service life, which translates into reduced annual maintenance costs. The lifetime decrease in roughness can lead to even more dramatic user cost savings. A case study demonstrated a fuel cost savings (for trucks alone) of $190,000 over a 10-year period for each lane mile of highway resurfaced under the special provision.

Pavement roughness affects the subjective quality of the ride for the traveler and also affects the cost of operating the vehicle. Less frequent resurfacing will reduce the owner agency's maintenance cost and the motorist's delay cost and will increase the motorist's vehicle operating cost. Analysis of a sample of Virginia Department of Transportation pavements indicates that the roughness of a pavement surface deteriorates—that is, increases—by about 1.23 in. per mile per year from the time it is placed until the time it is resurfaced. Recent reports from the WesTrack facility in Nevada, the Florida Department of Transportation, and the National Center for Asphalt Technology pavement test track in Alabama suggest that a gradual increase in roughness will mean a gradual reduction in fuel economy for the vehicles that use the road. Synthesis of these findings makes it possible to compare the maintenance cost to the owner agency against the travel time and operating costs to the motoring public, for maintenance resurfacing cycles of different lengths and for different initial roughnesses. This cost comparison finds that a decrease in the initial roughness of a new overlay reduces the sum of agency costs and user costs. Although a decrease in initial roughness apparently makes it feasible to prolong the resurfacing cycle, the cycle length that achieves the lowest total annualized cost (resurfacing cost plus delay cost plus fuel expense) remains largely the same: about 10 years. The trade-off between agency costs and user costs that the research findings imply is a caveat to the highway maintenance axiom, “Get in, get out, stay out!”

This paper summarizes the findings of a project that evaluated the procedures proposed by the Mechanistic–Empirical Pavement Design Guide (MEPDG) to characterize existing hot-mix asphalt (HMA) layers for rehabilitation purposes. A total of 33 cores were extracted from nine sites in Virginia to measure their dynamic moduli in the lab. Falling weight deflectometer (FWD) testing and visual pavement rating were performed at the sites, and the resilient modulus was measured in the laboratory. Selected cores were tested for their bulk densities and then for their dynamic moduli. The cores were broken down and tested for their maximum theoretical specific gravity. Finally, an ignition test was performed to find the percentage of binder and to reclaim the aggregate for gradation analysis. Volumetric properties were then calculated and used as input for the Witczak dynamic modulus prediction equations to find what the MEPDG calls the “undamaged master curve of the HMA layer.” The FWD data, resilient modulus data, and pavement rating were used to find the damaged master curve of the HMA layer as suggested for Input Levels 1, 2, and 3, respectively. It was found that the resilient modulus data needed for a Level 2 type of analysis (as proposed in Chapter 2 of the MEPDG) does not represent the entire HMA layer thickness, and therefore it was recommended that this analysis should not be performed. The use of Level 1 data is recommended because FWD testing appears to be the only procedure investigated that can measure the overall condition of the entire HMA layer.

In this paper, the accuracy of ground-penetrating radar (GPR) for estimating pavement layer thicknesses is studied on the basis of the investigation of 17 pavement sites in Virginia. The considered sites have different types of pavement systems (flexible, continuously reinforced, jointed concretes, and composite) and different ages (0 to 5 years; 10 to 15 years; older than 20 years with a surface less than 10 years; and older than 20 years with a surface older than 10 years). Because of the diversity of the test sections considered, the accuracy of the GPR thicknesses was studied for pavement age for the same type of pavement and against pavement type for sites of the same age category. For flexible pavements, the GPR thickness error was found to increase as the pavement's age increased (4.4% error for pavements 0 to 5 years old versus 5.8% error for pavements older than 20 years with surfaces older than 10 years). Moreover, for the same age category, flexible pavements were found to have a relatively high thickness error (4.4%) compared with the continuously reinforced concrete pavements (3.0%) and with the jointed plain concrete pavements (2.3%) because of the relative homogeneity of concrete for electromagnetic wavelength when compared with the different dielectric profile of aged hot-mix asphalt layer.

Different techniques for measuring pavement surface macrotexture and their application in pavement management are discussed. The main applications of surface macrotexture are to measure the frictional properties of the pavement surface and to detect hot-mix asphalt (HMA) construction segregation or nonuniformity. Since surface macro-texture can be measured quite efficiently using noncontact technologies and provides important information regarding pavement safety and HMA construction quality, this parameter may be included in the quality assurance or control procedures. Correlations between different measuring devices were investigated utilizing different HMA wearing surfaces. Excellent correlation was found between the circular track meter and sand patch measurements. In addition, the macrotexture determined using a laser profiler correlates well with that determined with sand patch measurements. Consistent with previous studies, it was found that the skid number gradient with speed is inversely proportional to the pavement macrotexture. However, there was a noticeable difference in speed dependency when smooth and ribbed tires were used. Oscillations in the percent normalized gradient with time due to seasonal variations were also observed. Macrotexture measurements hold great promise as tools to detect and quantify segregation for quality assurance purposes. A standard construction specification was proposed in a recent NCHRP study. However, the equation proposed for computing the nonsegregated estimated (mean) texture depth could not be applied to the mixes studied. An alternative equation has been proposed, which estimates the surface macrotexture using the mix nominal maximum size and voids in the mineral aggregate. The study was based on the mixes used at the Virginia Smart Road. Further investigation using other mixes is recommended.

A contemporary survey of bridge ride quality is described, and use of the survey to support the development of a modern smoothness provision for bridge decks is discussed. The survey found that bridges have an average of 60% more roughness than most mainline highway pavements [as measured by use of the international roughness index (IRI)]. However, a secondary analysis revealed that beam and girder camber can easily contribute more than 1000 mm/km of additional IRI roughness, which suggests that IRI may not be an equitable tool for measurement of the construction quality of bridges. This finding led to an additional analysis that focused on the use of a simulated rolling straightedge as a tool to control smoothness. Ultimately, the study demonstrated how inertial (and high-speed) profiling equipment can be applied to control bridge deck roughness through the use of a simulation that mimics the traditional 3-m straightedge.

In the summer of 1996 the Virginia Department of Transportation (VDOT) initiated the pilot of a new special provision regarding the smoothness of asphalt pavement surfaces. This special provision is based on the international roughness index (IRI) and is administered with a laser-equipped South Dakota–style inertial road profiler. A critical assessment of the nontraditional equipment and methods used to administer the special provision is provided. Issues addressed in the critique include provision exemptions, the ability to identify and contend with construction variability, and peculiarities of the equipment that affect the ability of VDOT to administer a modern acceptance provision.

A study was conducted to identify the predominant factors that affect the achievable smoothness of asphalt overlays. The subject was approached from the perspective of a contracting entity (state highway agency). The basis of the study was a roughness survey that incorporated 4270 lane-km (2,650 lane-mi) and two full construction seasons with hot-mix asphalt concrete paving. Among the variables found to be related to the achievable smoothness were the functional classification (highway system), original surface roughness, and a special provision for smoothness. Variables that were found to be not significantly related to the smoothness achieved included surface mix type, the application of additional structural layers, the use of milling, and time-of-day restrictions on construction activities (i.e., nighttime paving).

Transportation agencies are developing procedures and guidelines for managing the quality of pavement data collected to ensure the data meet the needs of the pavement management process. This study reviews the quality management practices being employed by public highway agencies for automated, semi-automated, and manual pavement data collection and delivery. Information was gathered through literature review, surveys of U.S. state and Canadian province public agencies and private contractors, and selected interviews.

In 1990, the Virginia Department of Transportation (VDOT) purchased its first South Dakota-type inertial road profiler. At that time, the profiler’s primary function was to collect data required for the Federal Highway Administration’s Highway Performance Monitoring System. By early 1995, however, the need to collect initial smoothness data safely, efficiently, and more accurately led VDOT to look to inertial profilers as a replacement for the California-type profilograph. In 1996, VDOT introduced a new special provision for smoothness, one that incorporated high-speed profilers and the International Roughness Index. In addition to chronicling those initial efforts, this paper discusses factors associated with achievable smoothness, as well as some deficiencies identified in the first generation of the new specification. The discussion them moves to a second generation of development, which focuses on enhancing the incentive/disincentive component of the specification, revising the smoothness targets, and reducing the pay lot size to combat excessive variability in ride quality.

In 2003, Virginia launched an expanded commitment to stone-matrix asphalt (SMA). Bye the end of 2004, contracts that encompassed nearly 400,000 tons of SMA Virginia’s 2003/2004 SMA “implementation initiative.” It summarizes and presented detailed information on costs and quantities, volumetric properties, compaction, permeability, and initial function characteristics (ride and friction) for SMA pavements placed during the two-year timeframe. The data presented in this work will be used to form the baseline for future pavement and materials evaluation.

This paper compares pavement macrotexture measurements obtained using the volumetric method and three laser-based devices. The study used data from a controlled experiment conducted at the Virginia Smart Road, as well as samples of in-service highway and airport surfaces. The data collected at the Virginia Smart Road, a controlled-access two-lane road that includes various hot mix asphalt (HMA) and concrete surfaces, were used for the main analysis. The other two sets of data were used for verification and validation of the model developed. The analysis of the data collected at the Virginia Smart Road showed that the Circular Texture Meter (CTMeter) mean profile depth (MPD) had the highest correlation with the volumetric (Sand Patch) mean texture depth (MTD). Models for converting the laser-based texture measurements to an estimated MTD were developed. The developed model was tested using measurements collected on several other highway and airport surfaces and with positive results.